• Olejnik, Lech
• Lipińska, Marta
• Lewandowska, Małgorzata

Abstract

The present study concerns the issues of the detailed microstructure evolution, development of grain boundariesand mechanical properties of commercially pure aluminium processed using multi-turn Equal Channel AngularPressing (mtECAP) and upsetting processes. Both processes cause a refinement of microstructure in coarsegrainedmaterials, though the deformation paths differ. This results in differences in microstructure, the distributionof grain boundaries, and mechanical strength and fractures. Four passes of mtECAP with a channelangles of φ = 90°, route C, caused a grain refinement of 1–1.2 μm and a fraction of HAGBs in a range of41.3–53.1%, depending on the plane examined. Upsetting from a height 26 mm to 3 mm caused higher averagegrain size and a lower fraction of HAGBs in particular planes. The mechanical strength was lower, but theapplied strain in this sample was also much lower than for the sample processed with mtECAP. Only combiningthe two processes resulted in an ultrafine grain structure with an average grain size of below 700 nm in the X andY planes. The results show that this hybrid process results in a plate with low anisotropy of tensile properties andwith the tensile strength close to 200 MPa.

Topics

• grain
• grain size
• aluminium
• strength
• tensile strength
• pure aluminum
• commercially pure aluminium